Hydraulic press speed control mechanism



FRANCIS.. J. NOW BY CHANGE OF NAME TO May 20, 1952 KA-rz FRANCIS J. KENT HYDRAULIC PRESS-SPEED CONTROL MEC Filgd Sept. 25, 1946 HANISM .4 Sheets-Sheet 1 A TTONEYS 0mm Us m 2&m Mm www A .NDS M 3 w1@ @LJI 2. n .u Y n.. i. @P N Q. 2, m. m Alnom a rru Al NOW BY CHANGE OF NAME TO FRANCIS J. KENT y HYDRAULIC PRESS SPEED CONTROL MECHANISM Filed Sept. 25, 1946 4 Sheets-Sheet 2 May 20, 1952 FRANCIS' J. KATz 2,596,988

A? 7' TOP/VE YS May 20, 1952 FRANCIS J. KA-rz 2,596,988

Now BY CHANGE oF NAME To FRANCIS J. KENT HYDRAULIC PRESS SPEED CONTROL MEcHANIsM Filed Sept. 25, 1946 4 Sheets-Sheet 5 INVENTOR. FKA/vos J. A/Arz ,vow ar c//A/vas aF MmeI ra FRANC/.s a. ,ve/vr A TTO/QNE YS May 20, 1952 A FRANCIS J. KA-rz 2,596,988

Now BY CHANGE oF NAME To FRANcls J. KEN-r HYDRAULIC PREss SPEED CONTROL MECHANISM SI'. K

8J INVEN TOR. FRANC/s .L Mrz Afa/r er c//A//af or NAMSY ra FKA/ms a. ,rs/vr @mw/#ALW Patented May 20, 1952 HYDRAULIC PRESS'y SPEED CONTROL MECHANISM Francis .L Katz, now uby change of name Francis .L Kenti Forest Hills,- N. Y,, assigner to Hydropress, Incorporated, New York, N. Y., a corpo- Application 'september v25, 1946', Serial-No. '699,1130

15'A Claims.

This invention relates to hydraulic presses and particularly to hydraulic extrusion presses with electrically operated control means controlling the speed otoperation of the press during the working stroke thereof.

In the extrusion of materials, such 'as high strength aluminum and magnesium alloys, it is desirable to control the extrusion so as to preven't certain defects in the extruded shapes. Asi' an example, cracks in the extruded material constitute 611e of the defects thatA might be caused by too fast an extrusion rate, and if the extrusion speed or rate is too slow, the process may become uneconomical.

Extrusion presses have been provided with vareious types of manual control valves operable by the press attendant during eachy stroke so as to adjust the rate of supply of liquid to the hydraulic cylinder bu-t it is apparent that such control is dimcult and dependent upon the skill and knowledge of the individual attendant. The speed, .for example, may change with variations in the metal, billet temperature cha-nge, and billet length.

One of the objects of thisl invention is tol in-' crease the operating efficiency and output ofl hydraulic presses and to improve the average qualpress is reached. This can be' accomplished by use of a balanced relay for operating the press control valve or by providing a balancingv voltageA of predetermined value. In the'la-ttercase; adelviation ofthe speed responsive voltage from the balancing voltage Will result in a potential Adif-- ference Which will cause 'current flow in a control circuit for regulation of the pressl control valve.

By either of these means, thej control thus can` be arranged so that the ramr v'vill` be operated ata predetermined speed during ther working stroke ofeach cycle.. f y y Another object of the invention. is topro'vi'de a simple electrical circuit for carrying out the control and in one mod'iii'cation thereof to .provide a circuit which; can'be compensated.foivai'iations inthe voltage used to balance the' voltage produced by the speed responsive means. In one form of the invention, the correction control rate is made proportional to the magnitude of the departure of the speed from a predetermined value.

These and other objects, features, and advantages lof the invention will become apparent from the following description and drawings which are merely exemplary.

In the drawings:

Fig-I. l is a fragmentary view partially in section of a metal extrusion press with two forms of speed regulating mechanism shown thereon for convenience, either one of which may be used as described hereafter.

Fig. 2 is an enlarged fragmentary View partially inVA section of one form of speed regulating mechanism operated by contact with the extruded material.v

Fig. 3 is a sectional view taken along the line 3 3 of Fig. 1, showing the control mechanism operable by means located on the ram'.

Fig. 4 isa sectional view taken along the line ll--il of Fig. 1,- showing the control mechanismk of Fig, 2;

Fig.- 5'1 is a diagrammatic View of a portion of the apparatus and one form' of electrical circuit ofthe Vcontrol mechanisms operated by the ram.

6A is al diagrammatic View of a portion of the apparatus and one form of electrical circuit of the control mechanism operable by contact with the extruded material.

Fig.Y 7 is a wiring diagram of one type of control circuit operable 'by either system (Fig. 5 or 6) to control the rate of movement ofrthe'ram'.

Fig. 8 is a wiring diagram of one form' of control circuit thatmay be used in place of thev circuit of Fig. '7.

Fig. 9 is a fragmentary sectional View of one typeof hydraulic control valve.

vSome-of the principal parts of a hydraulic press arefseen in Fig. l, wherein the main hydraulic cylinder 20 hasV high pressure liquid or fluid of a suitable character admitted thereto through pipe 2i. said iiuidv being controlled by valve 22 from supp-ly pipe ZSWhiC'lf-Lmay be connected to' a conventional hydraulic accumulator. Main ram 211 may have any type` of plunger 25` attached thereto which-is arranged to bereciprocable in billet container A2li.- Extr-usion die 21 is held in die support-28,` said die support being maintained in operating position by means of slideable wedge 29 which is vertically reci-procable by means of hydraulic mechanism 30. The die supportv 28 is moveable toits various positions by means ofhy` 3 draulic or similar mechanism 3|. The extruded stock is illustrated at 32 after it has passed through die 21 under the urgence of extrusion plunger 25. A pull-back or return ram 33 is movable by means of pull-back hydraulic cylinder 34 for the purpose of retracting the main ram In'prevous devices, the extrusion or working stroke of the ram had the speed thereof regulated by an adjustable manually operated valve in the supply line to the main hydraulic cylinder, the flow being cut down as the ram increases in speed due to decreased resistance.

In the embodiment shown herein, control valve 22 is operable by means of the multi-position main control lever 35 to govern the cycle of the press, all of the details of the valve not being shown inasmuch as they are conventional, one example of such a valve being seen in copending application Serial No. 505,110, filed October 6, 1943, now Patent Number 2,426,692. In the position shown in full lines in Fig. 1, the lever is set for admission of high pressure fluid to hydraulic cylinder 28 to produce the working stroke of the ram to force the metal in the billet container through .the extrusion die. At an intermediate position 36, the valve is set for prelling the hydraulic cylinder or moving the ram to its extruding position by a low pressure liquid at a speed many times greater than extrusion speed, this being used for the purpose of charging a billet into the billet chamber 26 in a conventional manner. A stop and a return position of the control lever are shown at 31 and 38, respectively.

In the fragmentary view of valve 22 (Fig. 9) the regulating valve portion thereof at 22 has a hydraulic fluid inlet port at 39 and an outlet port at 4|), said outlet port being connected to the main hydraulic cylinder supply pipe 2|. Valve 4| controls the iiow of hydraulic pressure in a well-known manner, the setting of valve 4| governing the rate of supply of fluid and, therefore,

the speed of the hydraulic ram. Valve 4| may be' adjusted relative to its seat by changing the position of rod 42, by the action of lever 43 and adjusting screw 44, said adjusting screw being operable by large gear 45 (Figs. l, 9), the large gear being rotatable by pinion 46 (Fig. 1) of control motor41. It is to be understood that other types of equivalent control valves may be used, the valve itself not forming a part of the present invention.

The electrical speed responsive means is operable in conjunction or in coordination with the movement of the ram. This may Ibe by means connected to the ram itself or by means contacting the work being extruded.

First, the control apparatus operable by means connected to the ram itself will be described. As mentioned previously, Fig. 1 for convenience shows both types of speed responsive operating means mounted on the press, only one normally being used. A track 48 (Figs. 1, 3, 5) is mounted on they cross-head 49 of ram 24 by means of brackets 50 and is movable therewith, the ram being shown in retracted position in dotted lines` at Tie rod 52 serves to hold platen 53 spaced relative to ange 54 of hydraulic cylinder 20 and rod 52 can carry the ram operated control mechanism shown generally at 55. The control mechanism comprises a roller 56 connected to a conventional tachometer generator 51 in some suitable manner such as by belt 6|. The roller 56 is supported on oscillatable arm 58, said arm bcing pivoted at 59 to the frame 66. A belt or driving means 6| is used to connect the roller 5,6 to the tachometer generator 51. A spring 62 holds the roller in a normally elevated position or a position wherein it will not contact track 48 as track 48 is moved under roller 56.

A switch 63 operable by lever 35 (Figs. 1 and 5), may be provided so as to complete the circuit to solenoid 64 when the operating lever is in position for the extrusion stroke of the ram. Solenoid 64 is connected to arm 58 by a link 64. In Fig. 5, operating lever 35 is shown in the extrusion stroke position and when in this position, switch 63 is closed so that current will iiow from power lead 64, switch 63, wire 69, magnetic switch coil 65, to push button 66. At the start of the extrusion stroke, push button 66 is depressed which will completeA the circuit to magnetic switch 66 and cause blades 61 and 68 thereof to close, thereby completing the circuit from switch 63, wire 69, switch blade 68, wire 18, solenoid 64, wire 1| back to power lead 12, thereby providing the holding circuit for the magnetic switch solenoid 65. Energization of solenoid 64 will cause Clockwise rotation of lever 58 (Fig. 5), thereby bringing roller 56 into Contact With track 48 which will cause rotation of roller 56 and operation of the tachometer generator 51. A speed indicating voltmeter |16 may be connected to leads 15. The voltage generated in leads 15 may be employed in the manner hereafter described to operate the control motor 41 of hydraulic regulating valve 22 so that the hydraulic iiuid will be supplied to the hydraulic cylinder 20 in accordance with the speed of the ram.

A control voltage related to the speed of the extrusion press also may be obtained from the movement of the extruded metal itself as will now be described. A roller 16 (Figs. 1, 4, and 6) is carried by frame 11, said frame being pivoted on rod 18 to platen 53. Tachometer generator 19 is mounted on frame 11 and is driven by belt 80, said belt in turn being driven by roller 16. The roller 16 and frame 11 are raised and lowered so that the roller can come in contact with the material being extruded. One way in which the lowering and raising can be accomplished is by attaching a cable to the wedge raising hydraulic cylinder cross-head 8|, -said cable passing over a pulley 82. When the wedge 29 (Fig. 6) is in its upper or non-extruding position, the roller 16 is raised up above the extrusion bed. When the wedge is placed in its lower position (broken lines, Fig. 6) so as to hold the extrusion die in place, cable 88 will take the broken line position 80 of Fig. 6 and the roller lowered so that it can make contact with the stock 83 as it is extruded. In this manner, the speed of extrusion of the stock is used to produce a voltage or electrical quantity at leads 84, which is proportional or related to the speed of said extrusion,

voltmeter 85 being provided similar to voltmeter |16 of Fig. 5. In this case it is not necessary to have a limit switch as for the device of Fig. 5,

inasmuch as there is no operation of the rollerv 16 and tachometer until the stock actually contacts the same.

Either of l the control voltages or electrical quantities produced by the tachometers of Fig. 5 or 6, may be employed to operate the circuit of Fig. '1 or 8 so as to change the adjustment of the hydraulic iiuid control valve and thereby adjust the speed of operation of the main ram or speed of the extrusion of the metal so as to maintain said speed at a predetermined value.

Referring to Fig. '1, the control voltage produced by the system of either Fig. 5 or Fig. 6 may be connected by leads 86 tothe solenoid 81" of thefloating voltage relay 881. Switchcontactlever' 89 is pivotedat its center and has contacts 90'- and 9| mounted thereon, there being spring 92 lconnected theretoin a conventional manner; Arm-ature 93 is affixed to lever 8'9 and is operable by solenoid 81. Reversing switch 94 has solenoids 95v and 96 for operating two setsv of contacts 91 and 98, respectively. Ata' given voltage or speed of the tachometer, switch lever 89 will be maintained in a position where neither contact 90 nor 9| is operable.

If, for example, the speed changes from apredetermined value in a direction such as to cause contact 90 to bel raised, magnet coil 95-wil1 be energized from power lead 99, through wire |00, solenoid Y95, contact 90, wire 'l0-l., to power lead |02. This will cause the set of contacts 91' to close and connect leads v|13l and llwith .leads |05 and |06, respectively, to cause the control motor |01 to rotate in a predetermined direction and thereby change the setting of regulating valve 22'.

The resistance 86 may be adjustable so as to permit adjustment of current in solenoid 81 so as to select the control speed.

In the event the control voltage fed to the leads 86 moves in the opposite directiony to tha-t just mentioned, contact 9|' will be raised and 90 will be lowered so that solenoid 96 will be operated to close the set of 'contacts 98. This will connect leads |03 and |64 toy |06 and |05 and thereby the power leads 99 and |102 in a-diierent direction than when contact 99 is closed to energize solenoid 95. There will thus be a control of motor |01 in a direction depending upon whether contact 90 or 9| isclosed.

After the speed of the ramor extruded metal has reached the predetermined value, switch arm 89 will take the neutral position shown in Fig. '1l and thereby stop the regulating motor.

A second form ofcontrol device for theregulate ing motor is shown in Figi. 8 whereinA three'generators of suitable types are.- indicated at' |08, |99, and I9, these generators being driven by a conmatically indicated at |30. The tachometer is shown at I l2 and this may be the` tachometer 5'1 or 19 of Fig. 5 or 6.` The regulating valve m'otor is shown at ||3 anda speed indicating'voltmeter at I Hl. The voltage generated by taohorneter |`|`2 is balanced by the voltage of generator ||-|l, tachometer |.2 being. connected to-wire I5, field I6 of generator ||i8,vwire4 |`|1, generator |'|`-0, and wire ||8. there is a potential differencev existent, will'furnish the excitation for'eld' lili`V of generator |08, generator |08 being connected through leads I9 and to the armature ofthe valve regulating motor H3.

Generator |09 is employed to furnishv excitation. for the iield |2| ofthe tachometer ||`2 and the field |22 of the valve operating motor ||3. Generator |09 is connected throughbus -|-23` to eld |2| and eldl |22, respectively. Inthis arrangement, the speed ofthe press or devicecony trolled may be chosen by setting of" variable ree sistance |26 in the fieldV |21 of generator' |'|'0 which will change the nca-flow current condition through eld IIS. 'I'he system will bein equilibrium when thetachometerrv generator voltage is balanced by thev Voltage of generator |10. The

excitation for the` valve operating motor and tachometer can be adjusted: by -meansof?v resistance |28 in the field winding |29 of"generator |09. It is evidentv that in` this arrangement, the reg- The resulting currentA ow therethrough, if'

ulating action of valve operating motor ||3 will! be governedboth in direction and in proportion tol the magnitude of deviation of the extrusion speed from a predetermined valve. lIn other words, the higher the speed above or'below a predetermined value, the faster will the valve regulating motor be operated to anew setting because the field in H6 will be stronger with a greater departure.

The control system described Vherein is' especially adapted for hydraulic presses used for'di'fierent purposes wherein it is desired thatA the operation of the presstakeplace ata constantrate ofspeed and provides a simple electrical circuit2 for accurately maintaining the speed' lof the ram at said predetermined value.

It is apparentz that variations may be made in the forms of the device show-n without depart.- ing from the spirit of they invention as dened in the appended claims What is claimed:

1. Ina hydraulic press, thecombinatio-n includving a fra-me, a hydraulic cylinder on said frame, a ram reciprocable in said cylinder and movable through a workin-g stroke--by'hydraulic pressurein said cylinder, work forming means-on said frame and operated upon byv said ram, regulata-ble fluid supply mea-ns for said cylinder, electric: voltage producing speed responsive 'meansoperablefin coordination with the movementof said: ram, and means connected-1 to said `regulatalole uid supply means and with said speed responsivefrneansop-v erable in accordance with the voltage-of said speed responsive means to regulate said fluid supply system whereby theA movementlof said ram relative to said forming meansis maintained constant during each working stroke thereof..

2. In a hydraulic press,V the: combination in.- cluding a frame, av hydraulic; cylinder onA said frame, aram reciprocable 'in said. cylinder and movable through aworking-'stroke by hydraulic pressure in said cylinder, workformingmeans` on said frame and operated upon-lbyfs'aid: ram,.regu' lata-ble fluid supply -means for said cylinder, electric voltageproducing speedresponsive means operable in coordinationwith. thernovrementfofVA said' ram, and means connected to: said' .regulatable fluid supply meansff and with sai'dspeed responsive means operable when said voltage vVaries from a predetermined value to' regulate said .fluidi sup-v ply system whereby thel movementy of saidlram relative to said forming meansv is: maintained constant during each working stroke thereof.

3. In a hydraulic press, the combinationincluding a frame, a hydrauli'ocylinder on Ysaid frame, a ram reciprocable in said cylinder-and mov-able. through a working stroke by hydraulic pressure in said cylinder, work forming| means on. said frame and operated upon by vsaid ram,V regulatable fluid supply means for said cylinder,- electri'crvoltage producing speed responsive means operatively connected to said ram., and 'meansv connected with` said reg-ulatable fluid supply meansv operable when said voltage varies from a predetermined value to regulate said fluid supplyl system whereby the movement ofA saidram relative; to said forming means is maintained constant during each working stroke thereof.

4. In a hydraulic' press, theoombin'ation including a frame, a hydraulic; cylinder'on said frame, a ram reciprocable in saidcylinder' and' 'movable through a'working stroke by hydraulic pressure in said cylinder, work forming? means onv said. frame and operated upon 'by saidra'm, fluid. supply means for said cylinder, velectr-ievoltages:pro-- ducing speed' responsive means mierateclllayxnovei ment of material acted upon by said ram, and means connected with said fluid supply means and the speed responsive means operable when said voltage varies from a predetermined value to regulate said fluid supply system whereby the movement of said ram relative to said forming means is maintained constant during each working stroke thereof.

5. In a hydraulic press, the combination including a frame, a hydraulic cylinder on said frame, a ram reciprocable in said cylinder and movable through a working stroke by hydraulic pressure in said cylinder, work forming means on said frame and operated upon by said ram, regulatable uid supply means connected to said cylinder, electric voltage producing speed responsive means operable in coordination with the movement of said ram, balancing means connected to said fluid supply means to regulate said fluid supply system, said balancing means being connected with said speed responsive means and energizable when said voltage produced by said speed responsive means deviates from a predetermined standard, whereby movement of said ram relative to said forming means is maintained constant during each Working stroke thereof.

6. In a hydraulic press, the combination including a frame, a hydraulic cylinder on said frame, a ram reciprocable in said cylinder and movable through a Working stroke by hydraulic pressure in said cylinder, Work forming means on said frame and operated upon by said ram, uid supply means for said cylinder, electric voltage producing speed responsive means operable in coordination with the movement of said ram, a floating relay operable by said speed responsive means, and means connected With said fluid supply means controlled by said relay and operated when said voltage varies from a predetermined value to regulate said fluid supply means whereby the movement of said ram relative to said forming means is maintained constant during each Working stroke thereof.

'7. In a hydraulic press, the combination including a frame, a hydraulic cylinder on said frame, a ram reciprocablein -said cylinder and movable through a working stroke by hydraulic pressure in said cylinder, work forming means on said frame and operated upon by said ram, fluid supply -means for said cylinder, electric voltage producing speed responsiveA means operable in coordination with the movement of said ram, a voltage source of predetermined value connected to said speed responsive means for balancing said speed responsive means voltage when said responsive means is operated at a predetermined speed, and means connected with said uid supply means and controlled by the resultant current when the speed deviates from a predetermined value to regulate said fluid supply system whereby the movement of said ram relative to said forming means is maintained constant during each working stroke thereof.-

8. In a hydraulic press, the combination including a frame, a hydraulic cylinder on said frame, a ram reciprocable in said cylinder and movable through a working stroke kby hydraulic pressure in said cylinder, Work forming means on said frame and operated upon by said ram, fluid supply means for said cylinder, electric voltage producing speed responsive means operable in coordination with the movement of said ram, a motor operated regulating valve for said fluid supply means, a generator connected to said regulating valve motor, means connecting said speed responsive means to a source of predetermined voltage through the fleld of said generator, 4whereby when the voltage produced by said speed responsive means deviates from a predetermined value, a current will flow through said eld to operate said regulating valve to regulate the fluid supply to maintain movement of said ram relative to said forming means constant during each working stroke thereof.

9. In a hydraulic press, the combination including a frame, a hydraulic cylinder on said frame, a ram reciprocable in said cylinder and movable through a working stroke by hydraulic pressure in said cylinder, work forming means on said frame and operated upon by said ram, fluid supply means for said cylinder, electric voltage producing speed responsive means operably connected to said ram, a floating relay operable by said speed responsive means, and means controlled by said relay and operated when said voltage varies from a predetermined value to regulate said fluid supply means whereby the movement of said ram relative to said forming means is maintained constant during each working stroke thereof.

10. In a hydraulic press, the combination including a frame, a hydraulic cylinder on said frame, a ram reciprocable in said cylinder and movable through a Working stroke -by hydraulic pressure in said cylinder, Work forming means on said frame and operated upon by said ram, fluid supply means for said cylinder, electric voltage producing speed responsive means operable by said ram, a voltage source of predetermined value connected to said speed responsive means for balancing said speed responsive means voltage When said responsive means is operated at a predetermined speed, and means connected With said uid supply means controlled by the resultant current when the speed deviates from a predetermined value to regulate said fluid supply system whereby the movement of said ram relative to said forming means is maintained constant during each working stroke thereof.

. 11. In a hydraulic press, the combination including a frame, a hydraulic cylinder on said frame, a ram reciprocable in said cylinder and movable through a Working stroke by hydraulic pressure in said cylinder, Work forming means on said frame and operated upon .by said ram, fluid supply means for said cylinder, electric voltage producing speed responsive means operatively connectable with material acted upon by said ram and operable by movement of said material, a voltage source of predetermined value connected to said speed responsive means for balancing said speed responsive means voltage when said responsive means is operated at a predetermined speed, and means controlled 'by the resultant current when the speed deviates from a predetermined value to regulate said fluid supply system whereby the movement of said ram relative to said forming meansis maintained constant during each Working stroke thereof.

1'2. In a hydraulic press, the combination including Va frame, a hydraulic cylinder on said frame, a ram reciprocable in said cylinder and movable through a working stroke by hydraulic pressure in said cylinder, Work forming means on said frame and operated upon by said ram, fluid supply means for said cylinder, electric voltage producing speed responsive means operable by movement of material acted upon by said ram, a motor operated regulator for said fluid supply means, a generator connected to said regulating accesso" sponsive means to a source of predetermined voltage through the eld of said generator whereby when the voltage produced by said speed responsive means deviates from a predetermined Value, a current will iiow through said iield to operate said regulating valve and regulate the fluid supply and thereby maintain movement of said ram relative to said forming means constant during each working stroke thereof.

13. In a hydraulic press, the combination including a frame, a hydraulic cylinder on said frame, a ram reciprocable in said cylinder and movable through a working stroke by hydraulic pressure in said cylinder, Work forming means on said frame and operated upon by said ram, uid supply means for said cylinder, electric voltage producing speed responsive means operable in coordination with the movement of said ram, a motor controlled fluid supply valve, and means connected to said motor control valve to operate the same in a direction and at a rate in proportion to the magnitude of the departure of the voltage produced by said electric voltage producing speed responsive means from a predetermined value.

14. In a hydraulic press, the combination including a frame, a hydraulic cylinder on said frame, a ram reciprocable in said cylinder and movable through a working stroke by hydraulic pressure in said cylinder, work forming means on said frame and operated upon by said ram, uid supply means connected to said cylinder. a regulatable uid supply control means in said supply means, electric voltage producing speed responsive means, a connection between said speed re.

sponsive means and said ram to drive said speed responsive means and produ-ce a voltage, and means connected to said fluid supply control means and said speed responsive means operating said control means when the voltage produced by the speed responsive means varies from a predetermined value to regulate the iiuid supply 10 system so as to maintain the ram speed constant during each working stroke thereof.

15. In a hydraulic press, the combination including a frame, Va hydraulic cylinder on said frame, a ram reciprocable in said cylinder and movable through a working stroke by hydraulic pressure in said cylinder, work forming means on said frame and operated upon by said ram, uid supply means connected to said cylinder, a regulatable uid supply control means in said supply means, elctric voltage producing speed responsive means, a connection between said speed responsive means and said ram to drive said speed responsive means and produce a volta-ge, said connection being movable to operative position during the working stroke of the ram, and means connected to said 'uid supply control means and said speed responsive means operating said control means When the voltage produced by the speed responsive means varies from a predetermined value to regulate the fluid supply system so as to maintain the ram speed constant during each working stroke thereof.

FRANCIS J. KATZ.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 404,726 Nickerson June 4, 1889 695,220 Lyndon Mar. 11, 1902 1,671,463 Boddie May 29, 1928 1,833,048 Cutler Nov. 24, 1931 2,051,018 Umansky Aug. 11, 1936 2,113,208 Andrews et al Apr. 5, 1938 2,258,462 Martin Oct. 7, 1941 2,325,190 McElhinney- July 27, 1943 2,325,401 Hurlston July 27, 1943 2,387,532 Schenk Oct. 23, 1945 2,426,692 Katz Sept. 2, 1947 

